The planets of life

Astrobiology is the study of the origin, evolution, distribution, and future of life in the universe. We are looking at the connections between the thermal evolution and state of planets and the ability of these to host life.

The word "Habitability" comes from the Latin word "habitare", which means to dwell. It describes a system, in our case a planetary object that can sustain (not necessary create) life over long timescales. This system has to regulate the climate, provide and recycle nutrients, be stable enough to allow survival, but still be dynamic enough to be able to adapt to changes endangering life. But what are the conditions life needs?

The Earth is the only planet we know that harbours life. We have been looking with robotic missions on Mars and astronauts took samples from the Moon, but we did not yet find convincing evidence that there might be life on these objects. But is there life on other planets, maybe life we simply didn’t detect yet? Or are we the only place where life could flourish? We want to understand how thermal evolution, interior structure, mass and chemistry, and the planet’s host star influence the so called "Habitability" of a planet.

Thermal evolution and habitability

The thermal evolution does not only influence the geologic features and processes that shape the planet, it also changes the ability of a planet to support life. Especially plate tectonics might be a necessity to support the evolution of complex life. The model below shows the complex interaction between plate tectonics, magnetic filed, outgassing and biosphere.

Plate tectonics versus One-plate convection

Interior structure, composition and habitability

The chemical composition and the interior structure influence the thermal evolution and the reservoir of elements necessary to form an atmosphere or to sustain life. Each planet obtains its bulk elements by its host-star and evolves a specific composition and interior structure after an individual thermal evolution. We want to know whether - and if yes how - outgassing, crustal formation and mineralogy of a planet depend on the host star and the planet’s mass and how this again influences the habitability of the planet.

Inhabited without habitants

It has been suggested that life itself may reshape the internal evolution of a planet. If this suggestion is true one can pose the question: Can a planet be habitable without being inhabited? To be more precise: is life necessary to create a habitable environment? Was it a co-evolution and would our planet change completely if there was no life, would maybe even plate tectonics cease if there were no organism at all on Earth?